Last night’s aurora was the best in years for the northern U.S. and southern Canada. What began as an amorphous arch of light in the northern sky around 8:30 p.m. evolved into spears of pale green light that shot nearly to the zenith. At the same time, brilliant yellowish curtains fluttered just above the northern horizon. What a night! I reluctantly went to bed around 12:30 with aurora still simmering behind silhouetted trees. Every time the display seemed to be subsiding, another ray or three would suddenly appear and stop me in my tracks. The BIG question is – will it happen again tonight? Maybe. The Space Weather Prediction Center is forecasting more storming through the 13th.
All this activity is connected to storms from big sunspot group 1164, which today moved to the sun’s backside, and particles streaming earthward from recent coronal holes
A look at the Kp index and plot of the auroral oval tells the story of last night’s display. You can see that the oval – the seat of the aurora – edged across the northern U.S. and into the northern sky. The oval expands and contracts in response to solar activity. Most of the time it’s snugged up around Hudson Bay, but last night it expanded southward into North Dakota, Minnesota, Wisconsin and Michigan. When the Kp index, a marker of magnetic activity, reaches 5 or higher, magnetic storm-level activity and accompanying aurora wreak beautiful havoc.
I’ll always try to update when a storm might be or is happening, but it’s always a good idea – especially when the sun exhibits large sunspot groups and flares – to head over to the NASA POES site to see what the oval’s up to. You can check the Kp-index as well. Is a tall red bar up? Well, it might time to put on your coat and walk out the door for a look-see.
If you photographed last night’s aurora, I’d love to share your images with our readers. Please send them to me at: email@example.com Thanks!